One of Australia's biggest banks, ANZ, said Friday it would fight allegations of "cartel conduct" by federal prosecutors over a massive capital-raising drive to meet tougher regulatory requirements.

The charges, to be laid by the Commonwealth Director of Public Prosecutions (CDPP), come at a torrid time for Australia's top banks as a royal commission looks into misconduct in the finance industry.

ANZ in 2015 raised Aus$2.5 billion (US$1.9 billion) from institutional investors in a share placement, and up to Aus$500 million from retail investors.

After an investigation by the Australian Competition and Consumer Commission (ACCC), the consumer watchdog claimed there were "cartel arrangements relating to trading in ANZ shares" following the institutional share placement.

Prosecutors will allege there was "an arrangement or understanding allegedly made" by the joint lead managers of the bank's institutional equity placement of some 80.8 million shares in August 2015, ANZ said.

The lender, its Group Treasurer Rick Moscati, two other firms and a number of other individuals would be charged over the alleged criminal cartel conduct, the ACCC said.

"It will be alleged that ANZ and the individuals were knowingly concerned in some or all of the conduct," ACCC Chairman Rod Sims said in a statement Friday.

According to the ACCC, cartel conduct is deemed to have taken place when businesses act together, instead of competing against each other, to drive up the profit of cartel members.

There was no immediate comment from the CDPP.

ANZ chief risk officer Kevin Corbally said the Australian-listed company "acted in accordance with the law in relation to the placement and on that basis the bank intends to defend both the company and our employee".

ANZ said it was also cooperating with an investigation by the corporate regulator, the Australian Securities and Investments Commission, that the bank should have told the market the joint lead managers took up some 25.5 million shares of the placement.

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